Can Delayed Period And Navel Pain Be Due To Appendicitis?

Hi Doctor, A female friend of mine is delayed for 18 days now..she has very sharp pain below naval intermittently throughout the day,ideally it should be due to pregnancy,but the pain is unbearable...She would be undergoing various test for appendicities,Pls clear my doubts..what are the chances and can the delay periods be due to appendicities..

Friends Age-24-ht-5.7-wt-65-has been having regular delays of 2-3 days